GB2565904A

GB2565904A - Obstetric forceps

Info

Publication number: GB2565904A
Application number: GB1810956.1A
Authority: GB
Inventors: Jessup Mark
Original assignee: Surgical Dynamics Ltd
Current assignee: Surgical Dynamics Ltd
Priority date: 2017-11-03
Filing date: 2018-07-04
Publication date: 2019-02-27
Anticipated expiration: 2038-07-04
Also published as: GB201810956D0; GB201718271D0; WO2019086904A1; GB2565904B

Abstract

A pair of obstetric forceps has two elongate members having a blade 12, a shank 18 and a handle 14. Each handle is slidably mounted on a shank and is coupled thereto via a biasing means such as a spring 28 such that a pull force on the handle displaces it with respect to the shank and compresses the spring. The displacement is measured by an electronic sensor, and a user is alerted if the displacement (proportional to the applied force) exceeds a predetermined level. The sensor may be a potentiometer 32 in the handle with a sliding contact on the shank, or a rotary encoder with a rack and pinion, or a capacitance linear encoder. The alert may be one or more LED lights which may be coloured, and/or a speaker, and/or a haptic indicator such as a vibrating motor, and/or a graphic display (figure 9). Two different alerts may indicate different force thresholds. The visual display may show the total force applied over time.

Description

Obstetric Forceps

Field of the Invention

The present invention relates to obstetric forceps which include sensors for monitoring traction force applied to the head of a baby and provide feedback to a user.

Background of the Invention

Obstetric forceps are surgical instruments used for assisting in the birth of a baby. Conventional forceps comprise two curved blades which are positioned around the baby’s head. The blades are locked together and then a medical professional applies a traction force in order to pull the baby through the birth canal during delivery. Sufficient force needs to be applied to move the baby. If insufficient force is applied, then the use of obstetric forceps can be prematurely abandoned in favour of an alternative, more invasive means of delivery. However, excessive traction forces can result in injury to both the baby and the mother.

The amount of force applied is subject to the judgement of the medical professional operating the forceps.

Systems that monitor the amount of traction force applied when using obstetric forceps are known. W02004/108010 describe obstetric forceps with a pull-sensing handle grip. The forceps include an electronic strain gauge and a wireless connection to a computer. US2011/0245865 describes obstetric forceps which include both an electronic strain gauge to measure the pulling force, and a number of pressure sensors to measure the compression forces applied by the forceps blades to the baby’s skull during the delivery process. The detected force data is then wirelessly transmitted to a computer. In both of these systems, the medical professional is required to look at the computer to gauge the amount of pull being exerted on the baby’s head by the forceps. These types of system are complex to use and add to the amount of equipment required in a delivery room.

WO2011/131988 describes obstetric forceps which measure the amount of pulling force using a mechanical force indicator and comprise means for mechanically disabling the handle of the device when a threshold force is exceeded. The mechanical force indicator includes a visual indication of pulling force in the form of a rotating barrel with differently coloured portions, each of which are indicative of a pre-selected range of pulling force.

It would be desirable to provide improved obstetric forceps.

Summary of the Invention

According to the invention there is provided a pair of obstetric forceps, comprising: a pair of curved blades for grasping a baby’s head during a forceps delivery, each blade connected to a shank; and a pair of handle portions;

wherein each handle portion is slidably mounted on a respective shank with a biasing means mounted within each handle portion, the biasing means arranged to engage both the handle portion and the shank such that a force exerted on the handle portion is transferred to the shank by the biasing means;

wherein each shank includes means for locking the blades together at a point between the blades and the handle portions such that the handle portions are aligned;

wherein the forceps include an electronic sensor arranged to measure electronically the extent of displacement of at least one of the shanks relative to the respective handle portion when a pulling force is applied to the handle portions during a forceps delivery;

and wherein the forceps further include means for alerting a user if the extent of displacement of the shank relative to the handle portion exceeds a predetermined level.

The electronic sensor may comprise a potentiometer and a sliding contact, wherein at least one of the handle portions is provided with the potentiometer and the respective shank is provided with a sliding contact, the potentiometer and sliding contact arranged to measure electronically the extent of displacement of the shank relative to the handle portion when a pulling force is applied to the handle portion during a forceps delivery. Preferably, the potentiometer measurement is proportional to the magnitude of the pulling force applied to the handle portions.

The magnitude of the pulling force applied to the handle portions can be calculated from the potentiometer measurement. The predetermined level of the extent of displacement to the shank relative to the handle portion is equivalent to a predetermined level of pulling force.

The electronic sensor may comprise a rotary encoder in combination with a rack and pinion, wherein at least one of the handle portions is provided with a pinion mounted on a rotary encoder and the respective shank is provided with a complementary rack, wherein the rotary encoder and rack and pinion are arranged to measure electronically the extent of displacement of the shank with respect to the handle portion.

The electronic sensor may comprise a capacitance linear encoder or an optical linear encoder.

Preferably, the means for alerting a user that the extent of displacement of the shank relative to the handle portion during a forceps delivery exceeds a predetermined level includes a visual indicator.

Preferably, the visual indicator is adapted to provide an indication of the amount of force being applied to the head of the baby.

Preferably, the visual indicator comprises at least one light. The visual indicator may include at least one coloured light.

Preferably, the visual indicator comprises at least two different coloured lights, configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range; and a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion exceeds the preferred range.

Alternatively, the visual indicator may comprise three different coloured lights, configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range; a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the preferred range, but lower than a predetermined maximum force; and a light of a third colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the predetermined maximum force.

Preferably, the or each coloured light is an LED. The at least one coloured light may be a multi-coloured LED.

A multi-coloured LED may be configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range; and a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion exceeds the preferred range.

Alternatively, a multi-coloured LED may be configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range; a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the preferred range, but lower than a predetermined maximum force; and a light of a third colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the predetermined maximum force. An LCD screen display may be used in preference to LEDs.

Preferably, the means for alerting a user that the extent of displacement of the shank relative to the handle portion exceeds a predetermined level includes a haptic indicator. The haptic indicator may be adapted to provide an indication of the amount of force being applied to the head of the baby.

Preferably, the haptic indicator is a vibrating motor. The vibrating motor may be configured such that the motor vibrates when the extent of displacement of the shank relative to the handle portion exceeds the preferred range. Alternatively, the vibrating motor may be configured such that the motor vibrates at a first speed when the extent of displacement of the shank relative to the handle portion is within a preferred range; and the motor vibrates at a second speed when the extent of displacement of the shank relative to the handle portion exceeds the preferred range. Preferably, the second speed of motor vibration is greater than the first speed of motor vibration.

The means for alerting a user that the extent of displacement of the shank relative to the handle portion exceeds a predetermined level may include a speaker configured to sound an audible alarm if the extent of displacement of the shank relative to the handle portion exceeds a predetermined level.

Brief Description of the Drawings

In the Drawings, which illustrate preferred embodiments of the invention and are by way of example:

Figure 1 is an isometric view of a pair of obstetric forceps according to the present invention;

Figure 2 is a plan view of the obstetric forceps of Figure 1, separated into two component parts;

Figure 3a is a side view of the obstetric forceps of Figure 1;

Figure 3b is a plan view taken along the section A-A marked in Figure 3a;

Figure 4 is an isometric view one of the parts of the obstetric forceps of Figure 1, with part of the handle casing removed;

Figure 5a is a partial side view of the part of the obstetric forceps of Figure 3, in a first position;

Figure 5b is a partial side view of the part of the obstetric forceps of Figure 3, in a second position, when a pulling force is applied to the handle;

Figure 6a is a partial plan view of the handle portion of a pair of obstetric forceps according to a further example of the present invention, the forceps shown with the casing removed, the forceps shown in a first position;

Figure 6b is a partial plan view of the handle portion of a pair of obstetric forceps of Figure 6a, shown in a second position, when a pulling force is applied to the handle;

Figure 7 is a partial side view of a first handle portion of the obstetric forceps of Figure 6a, shown with the casing removed;

Figure 8 is a partial side view of a first handle portion of the obstetric forceps of Figure 6a, shown with the casing intact;

Figure 9 is a partial plan view of a pair of obstetric forceps according to the present invention;

Figure 10a is a partial plan view of a first handle portion of a pair of obstetric forceps according to a further example of the present invention, the handle portion shown with the casing removed, the handle shown in a first position; and

Figure 10b is a partial plan view of the first handle portion of a pair of obstetric forceps of Figure 10a, shown in a second position, when a pulling force is applied to the handle;

Detailed Description of the Preferred Embodiments

Referring to Figure 1, there is shown a pair of obstetric forceps 10 according to the invention. The obstetric forceps 10 comprise two parts, each part having a blade 12a, 12b at one end and a handle 14a, 14b at the other end, each handle being connected to its respective blade via a respective shank 18a, 18b. Finger grips 16a, 16b extend from each handle 14a, 14b. Preferably, as illustrated, the blades 12a, 12b are fenestrated blades. When the forceps 10 are assembled, as shown in Figure 1, the finger grips 16a, 16b extend to opposite sides of the handle 14, so that a user of the forceps 10 can hook their fingers over the finger grips 16a, 16b to help exert a pulling force on the baby’s head. Each blade 12a,12b is curved to allow a firm grasp of the baby’s head. Figure 2 illustrates the two separate parts which join together to make the obstetric forceps 10. The forceps 10 are assembled by inserting each blade 12a, 12b separately into the birth canal, and aligning with the baby’s head. The two shanks 18a, 18b are then crossed at the midpoint 20 (shown on Figure 1) and locked together. In the illustrated example the shanks 18a, 18b are locked together via an English lock mechanism, however other lock configurations are possible.

Figure 3 illustrates the forceps of figure 1, with the upper part of the handle casing removed so that the inside of each handle 14a, 14b can be seen. As can be seen in Fig 3, the shank 18a, 18b of each part of the forceps 10 has a part 18a’, 18b’ which extends inside the hollow handle casing 14a, 14b. The shanks 18a, 18b are spring-mounted such that they can slide into and out of the handle casing 14a, 14b.

As shown in Figures 3 and 4, the internal part 18a’, 18b’ of each shank includes protrusion 27a, 27b which sits between the end wall of the casing 26a, 26b and an internal wall 25a, 25b within the handle casing 14a, 14b. The protrusion 27a on the first shank 18a’ may only move between the end wall 26a and the internal wall 25a. The protrusion 27b on the second shank 18b’ may only move between the end wall 26b and the internal wall 25b. In this way, movement of each shank is restricted. The protrusions 27a, 27b also prevent the shanks 18a, 18b from being removed from the handle casing 14a, 14b.

As shown in Figure 4, a spring 28a, 28b (springs 28a, 28b are identical) is coiled around the internal part of each shank 18a’, 18b’. The springs 28a, 28b are mounted between an enlarged annular portion 24a, 24b of each shank, and an annular opening 30a, 30b within the handle casing 14a, 14b, which provides a seat for the springs 28a, 28b. When a user pulls on the handles 14a, 14b, the handles move away from the blades 12a, 12b against the biasing force of the springs 28a, 28b, compressing the springs 28a, 28b between the enlarged annular portion 24a, 24b of each shank and the annular openings 30a, 30b within the handle casings 14a, 14b. The force applied to the baby’s head is determined by the spring constant of the springs 28a, 28b until the springs are fully compressed.

In this example, the electronic sensor for sensing displacement of the shank relative to the handle portion is a combination of a potentiometer 32 and a sliding contact 38. The potentiometer 32 is included within the first handle portion 14a, which also includes, batteries 34 and a printed circuit board 36 all located within the handle casing 14a. The sliding contact 38 which acts on the potentiometer 32 is attached to the shank 18a’. The potentiometer 32 is mounted in a static position inside the handle casing 14a, and the sliding contact 38 is mounted on the shank 18a’ and moves with the shank 18a. The potentiometer 32 changes its resistance according to the position of the sliding contact 38 and in this way measures the distance that the shank 18a moves with respect to the handle casing 14a when a user pulls on the handles 14a, 14b. Since the force exerted on the baby’s head is through the springs 28a, 28b, the signal issuing from the potentiometer is proportional to the force exerted on the baby’s head.

The first handle portion 14a may include a switch 48 which is activated when the two parts are assembled to form the forceps 10. The switch 48 is activated through direct contact with a part of the second handle 14b.

Figure 5a illustrates the position of the shank 18a with respect to the handle 14a when no pulling force is being applied to the handle. Figure 5b illustrates the position of the shank 18a with respect to the handle 14a when a pulling force is applied to the handles 14a, 14b in the direction of the arrow. When a pulling force is applied to the handles 14a, 14b the springs 28a, 28b are compressed and the sliding contact 38 moves along the potentiometer 32. The potentiometer measurement is proportional to the magnitude of the applied pulling force. When the pulling force is removed the springs 28a, 28b return the shanks 18a, 18b to their original position. Preferably, as shown in the example, only one of the handle casings

14a include a potentiometer 32, and only one of the shanks 18a is provided with a sliding contact 38.

In a preferred example, the handle casing 14b also includes an LED 40 and a vibrating motor 42 (as shown in Figures 4 and 5). Preferably the LED 40 is a multi-colour LED and preferably the LED 40 emits different colours depending on the amount of displacement of the shanks 18a, 18b with respect to the handles 14a, 14b, and hence amount of force being applied to a baby’s head through the handles 14a, 14b. For example, the LED 40 could be programmed to emit green light when the force applied to a baby’s head is within acceptable limits. The colour of the light emitted from the LED 40 could change to amber when the applied force is approaching a threshold force, and the colour of the light emitted from the LED 40 could change to red when the applied force exceeds a threshold force, giving an immediate visual indication to the medical professional that too much force is being applied. Alternatively, separate coloured LEDs could be used. For example, separate green, amber and red LEDs could each activated to light up with different applied forces. In the illustrated example the LED 40 is located inside the handle casing 14a but is viewable through a window 44 or a translucent portion of the handle casing 14a. An LCD display could be used instead of LEDs.

Where the forceps 10 includes a vibrating motor 42, this can be used to provide haptic feedback to the user. The vibrating motor 42 may be actuated when the applied force exceeds a threshold force, or when the applied force is close to a threshold force. The motor 42 causes the handle to vibrate and the vibrations will be felt by the hand holding the handles. The vibrations alert the medical professional that too much force is being applied. Alternatively, or additionally a speaker may be used to provide an audible alarm.

The handle casings 14a, 14b are preferably provided in two halves, one half of which is illustrated in Figures 4 and 5. The other half of the casing is preferably attached using either screws or pins (not shown) which fasten into respective bores 46 in the casing.

Figures 6a and 6b illustrate a partial plan view of a further example of the invention, where the electronic sensor is in the form of a rotary encoder 50 mounted in combination with a rack 54 and pinion 52. The pinion wheel 52 mounted on the rotary encoder 50 and engages with a complementary rack 54 which is mounted on the internal part of the first shank 18a’. The rotary encoder 50 is shown as transparent in the drawings to allow the pinion 52 to be seen. Figure 7 illustrates a side view of the first handle portion 14a with casing removed.

As with the previous example, the shank 18a, 18b of each part of the forceps 10 has a part 18a’, 18b’ which extends inside the hollow handle casing 14a, 14b. The shanks 18a, 18b are spring-mounted such that they can slide into and out of the handle casing 14a, 14b. Protrusions 27a, 27b similar to those described in relation to Figures 3 to 5 are also present in this example, restricting movement of each shank in the same manner.

As with the previous example, the internal part 18a’, 18b’ of each shank has an enlarged annular portion 24a, 24b located close to the end of the shank 18a’, 18b’. A spring 28a, 28b (springs 28a, 28b are identical) is coiled around the internal part of each shank 18a’, 18b’. The springs 28a, 28b are mounted between the enlarged annular portion 24a, 24b of each shank, and an annular opening 30a, 30b within the handle casing 14a, 14b, which provides a seat for the springs 28a, 28b. When a user pulls on the handles 14a, 14b, the handles move away from the blades 12a, 12b against the biasing force of the springs 28a, 28b, compressing the springs 28a, 28b between the enlarged annular portion 24a, 24b of each shank and the annular openings 30a, 30b within the handle casings 14a, 14b. The force applied to the baby’s head is determined by the spring constant of the springs 28a, 28b until the springs are fully compressed.

The rotary encoder 50 is mounted in a static position inside the handle casing 14a, and the rack 54 is mounted on the shank 18a’ and moves with the shank 18a. As the shank 18a moves, the pinion wheel 52 is turned by the rack. This in turn causes the rotary encoder 50 to rotate and provides an electrical output signal which is proportional to the distance the shank

18a moves with respect to the handle casing 14a when a user pulls on the handles 14a. 14b. Since the force exerted on the baby’s head is through the springs 28a, 28b, the signal issuing from the rotary encoder 50 is proportional to the force exerted on the baby’s head.

Figure 6a illustrates the position of the shank 18a with respect to the handle 14a when no pulling force is being applied to the handle. Figure 6b illustrates the position of the shank 18a with respect to the handle 14a when a pulling force is applied to the handles 14a, 14b in the direction of the arrow. When a pulling force is applied to the handles 14a, 14b the springs 28a, 28b are compressed and the pinion wheel 52 moves along the rack 54, turning the rotary encoder 50. The output of the rotary encoder is proportional to the magnitude of the applied pulling force. When the pulling force is removed the springs 28a, 28b return the shanks 18a, 18b to their original position. Preferably, as shown in the example, only one of the handle casings 14a includes the rotary encoder/rack and pinion arrangement.

As with the previous example, the handle casing 14b preferably also includes at least one LED 40 and a vibrating motor 42 and a battery 56. In this example (see Figure 7) three separate LEDs 40a, 40b, 40c are used, each with a different colour, for example green, amber and red, with each activated to light up with different applied forces. In the illustrated example the LEDs 40a, 40b, 40c are located inside the handle casing 14a but viewable through a window 44 or a translucent portion of the handle casing 14a.

As shown more clearly in Figure 8, one of the two handle portions 14a, 14b may include a locating protrusion 60 which locates into a complementary recess 62 located on the other handle portion. The forceps may also be provided with a battery pull-tab 70, the removal of which turns the forceps on.

The forceps illustrated in this example also include means for recording the measured force in the form of a removeable memory card, such as an SD card 58. The forceps may also include a controller for calculating the total force applied over time. This may also be recorded on the SD card 58.

It may be important to calculate the total force applied over time (total force = force x time, typically calculated as Newton minutes). Exceeding a predetermined maximum value of total force may lead to increased risk of internal maternal damage. This calculated value of total force can also be displayed to the user, for example as shown in Figure 9, where the calculation of total force is shown in the form of a digital progress bar 64. Application of a maximum desired value of total force would be indicated by a fully completed progress bar.

A coloured LED may also be used to indicate that a maximum threshold of total force has been reached. Alternatively, or additionally, where the forceps 10 includes a vibrating motor 42, this can be used to provide haptic feedback to the user, as previously described.. Vibrations may be used to alert the medical professional that a maximum threshold of total force has been reached. Alternatively, or additionally a speaker may be used to provide an audible alarm.

Typically, larger forces are required to be used with forceps on a patient undergoing a first vaginal delivery. Patients undergoing a second or subsequent vaginal deliveries typically require lower applied forces with forceps. In a preferred example, the forceps of the invention include the ability to switch between at least two different force modes in order to suit the patient’s circumstances. This means that the forceps may be set to alarm at a higher force threshold for a patient undergoing a first vaginal delivery, than a patient undergoing a second vaginal delivery.

Figures 10a and 10b illustrate a partial plan view of a further example of the invention, where the electronic sensor is in the form of a capacitance linear encoder. Like features have been labelled with like reference numerals. A first part 66 of the capacitance linear encoder is mounted within the handle portion 14a, this part of the encoder may for example comprise an etched copper plate on a printed circuit board. A second part 68 of the capacitance linear encoder is mounted on the end of the shank 18a’ inside the handle portion 14a. The second part of the encoder may also comprise an etched copper plate. The two parts 66, 68 are in contact. Each plate is etched with a pattern of lines. The second plate 68 attached to the end of the shank 18a’ and moves with the shank 18a, sliding over the first plate 66. As the two etched patterns pass over one another, different parts of the pattern come into contact and this provides a digital reading. In this way the distance moved by the shank 18a with respect to the handle casing 14a is measured by the capacitance linear encoder. Since the force exerted on the baby’s head is through the springs 28a, 28b, the signal issuing from the capacitance linear encoder is proportional to the force exerted on the baby’s head.

Figure 10a illustrates the position of the shank 18a with respect to the handle 14a when no pulling force is being applied to the handle. Figure 10b illustrates the position of the shank 18a with respect to the handle 14a when a pulling force is applied to the handles 14a, 14b in the direction of the arrow. When a pulling force is applied to the handles 14a, 14b the springs 28a, 28b are compressed and the second part 68 of the capacitance linear encoder mounted on the end of the shank 18a’ moves with respect to first part 66 of the capacitance linear encoder. The output from the capacitance linear encoder depends on the relative position of both parts of the encoder and is proportional to the magnitude of the applied pulling force. When the pulling force is removed the springs 28a, 28b return the shanks 18a, 18b to their original position. Preferably, only one of the handle casings 14a includes the capacitance linear encoder.

The capacitance linear encoder may be replaced with an optical linear encoder which includes a similar pair of etched plates. An LED and a photodetector detect the changes in light as the two plates pass over one another and this provides a digital reading.

Claims

1. A pair of obstetric forceps, comprising:

a pair of curved blades for grasping a baby’s head during a forceps delivery, each blade connected to a shank;

and a pair of handle portions;

2. A pair of obstetric forceps according to Claim 1, wherein the electronic sensor comprises a potentiometer and a sliding contact, wherein at least one of the handle portions is provided with the potentiometer and the respective shank is provided with the sliding contact, the potentiometer and sliding contact arranged to measure electronically the extent of displacement of the shank relative to the handle portion.

3. A pair of obstetric forceps according to Claim 1, wherein the electronic sensor comprises a rotary encoder in combination with a rack and pinion, wherein at least one of the handle portions is provided with a pinion mounted on a rotary encoder and the respective shank is provided with a complementary rack, wherein the rotary encoder and rack and pinion are arranged to measure electronically the extent of displacement of the shank with respect to the handle portion.

4. A pair of obstetric forceps according to Claim 1, wherein the electronic sensor comprises a capacitance linear encoder.

5. A pair of obstetric forceps according to any of Claims 1 to 4, wherein the means for alerting a user that the extent of displacement of the shank relative to the handle portion during a forceps delivery exceeds a predetermined level is a visual indicator.

6. A pair of obstetric forceps according to Claim 5, wherein the visual indicator is adapted to provide an indication of the amount of force being applied to the head of the baby.

7. A pair of obstetric forceps according to Claim 5 or 6, wherein the visual indicator includes at least one light.

8. A pair of obstetric forceps according to any of claims 5 to 7, wherein the visual indicator includes at least one coloured light.

9. A pair of obstetric forceps according to any of claims 6 to 8, wherein the visual indicator comprises at least two different coloured lights, and is configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range, and a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion exceeds the preferred range.

10. A pair of obstetric forceps according to Claim 8, wherein the visual indicator comprises three different coloured lights, configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range, a light of a second colour is actuated when the extent of displacement of the shank relative to the handle is greater than the preferred range, but lower than a predetermined maximum, and a light of a third colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the predetermined maximum.

11. A pair of obstetric forceps according to any of claims 8 to 10, wherein the or each coloured light is an LED.

12. A pair of obstetric forceps according to Claim 8, wherein the at least one coloured light is a multi-coloured LED.

13. A pair of obstetric forceps according to Claim 12, wherein the multi-coloured LED is configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range, and a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion exceeds the preferred range.

14. A pair of obstetric forceps according to Claim 12, wherein the multi-coloured LED is configured such that a light of a first colour is actuated when the extent of displacement of the shank relative to the handle portion is within a preferred range, a light of a second colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the preferred range, but lower than a predetermined maximum, and a light of a third colour is actuated when the extent of displacement of the shank relative to the handle portion is greater than the predetermined maximum.

15. A pair of obstetric forceps according to any preceding claim, wherein the means for alerting a user that the extent of displacement of the shank relative to the handle portion exceeds a predetermined level includes a haptic indicator.

16. A pair of obstetric forceps according to Claim 15, wherein the haptic indicator is adapted to provide an indication of the amount of force being applied to the head of the baby.

17. A pair of obstetric forceps according to Claim 15 or 16, wherein the haptic indicator is a vibrating motor.

18. A pair of obstetric forceps according to Claim 17, wherein the vibrating motor is configured such that the motor vibrates when the extent of displacement of the shank relative to the handle portion exceeds the preferred range.

19. A pair of obstetric forceps according to Claim 17, wherein the vibrating motor is configured such that the motor vibrates at a first speed when the pulling force measured by the potentiometer is within a preferred range, and the motor vibrates at a second speed when the pulling force measured by the potentiometer exceeds the preferred range.

5

20. A pair of obstetric forceps according to Claim 19, wherein the second speed of motor vibration is greater than the first speed of motor vibration.

21. A pair of obstetric forceps according to any preceding claim, wherein the means for alerting a user that the extent of displacement of the shank relative to the handle portion exceeds a predetermined level includes a speaker configured to sound an audible alarm if the 10 extent of displacement of the shank relative to the handle portion exceeds a predetermined level.